It is recognized that the spinal disc consists of three parts: first, the nucleus, a central portion that is a compression-resisting cushion; second, the annulus, a peripheral rim portion that is a tension-resisting hoop; and third, the end plates, the superior and inferior borders of the disc, consisting of the upper and lower surfaces of the vertebral body bones adjacent to the disc. Many studies have concluded that mechanical back pain is the most common and costly musculoskeletal condition affecting middle-aged humans in modern societies. Mechanical back pain may be caused by several factors, but overwhelming evidence suggests that degeneration of the spinal intervertebral disc, such as may be caused by Degenerative Disc Disease (DDD) is the most common condition causing back pain symptoms.
Many devices have been invented for the purpose of stabilizing and/or replacing parts of the disc in an effort to ease the pain associated with degenerative disc disease. Previous devices designed to treat DDD fall generally into the following four classes:
The first class includes rigid, three-dimensional geometric solid devices, either impervious or porous, that function as support struts. When these devices are placed between adjacent vertebral bodies they allow, and in some cases encourage bone to grow through and/or around the device to cause a bony fusion between two adjacent vertebral bodies. Rigid implants fabricated from metal, ceramic, or hard plastics suffer from several disadvantages such as: the need to create large surgical exposures disruptive to muscle and soft tissue, the need for large destabilizing entrance holes through the annulus of the disc, and the presence of large volumes of non-biologic material that reduce bone graft surface contact at the end plate.
The second class involves the use of semi-rigid artificial joints that allow motion in one or more planes. Examples include: U.S. Pat. No. 4,759,769 to Kostuik; U.S. Pat. No. 6,039,763 to Shelokov, and commercially available examples such as the Link device or the Charite Intervertebral Disc Endoprosthesis. These artificial joints have several disadvantages, including: the artificial joints are technically challenging to the surgeon in that proper placement of the device can be quite difficult, placement of the device requires large anterior exposures and re-operation procedures, if needed, are dangerous (life-threatening) due to anterior scarring and inability to use another surgical approach.
The third class is directed to non-rigid cushions designed to replace the nucleus of the disc. Examples of artificial discs are described in U.S. Pat. No. 4,904,260 to Ray, U.S. Pat. No. 4,772,287 to Ray and U.S. Pat. No. 5,192,326 to Bao. These devices are prone to wear and subsidence and as such pose a risk to the surrounding anatomy when they become dislocated out of the disc space.
Finally, the fourth class is the relatively new area of initially flexible, deployable containers that become rigid when injected with materials that can support loads. Examples include U.S. Pat. Nos. 5,571,189, 5,549,679 and 6,712,853 to Kuslich, the contents of which are incorporated in the entirety herein, each of which describe deployable, porous containers, useful in stabilizing a deteriorating spinal disc. The container is placed into a reamed out intervertebral space and is expanded by the introduction of graft material which may be tightly compacted within the container.
Like many other areas of surgery, spine surgery has become less invasive as smaller, more precise technology develops. Many minimally invasive intervertebral fusion devices exist, such as those disclosed in U.S. Pat. Nos. 5,571,189 and 5,549,679 and the commercially available XLIF® procedure by NuVasive. However, all minimally invasive fusion devices still require a surgical access opening that is as large as the device to be implanted. Generally speaking, the access aperture in minimally invasive procedures is at least 15-30 mm in diameter. Also, because minimally invasive procedures require direct visualization, the surgeon may need to cut bone and must significantly retract soft tissues and the nerve root, potentially causing nerve root injury or persistent post-operative pain.
By contrast, percutaneous surgery is done using x-ray visualization and image guidance and as such does not require resection of bony or soft tissue for direct visualization of the disc. Further, the incision is generally in the range of about 10 mm, much smaller than the access aperture in MIS procedures. Thus, percutaneous surgery results in a dramatic reduction in morbidity rates and more rapid recovery, both of which leading to significantly shorter hospitalization times.
U.S. Pat. Nos. 6,558,383 and 7,087,058 to Cragg describe a percutaneous method of fusing the lumbo-sacral region of the spine from an axial approach. The method and system described by Cragg are limited to fusing either the L5-S1 or the L4-L5-S1 motion segments using a rigid device and are further limited to an axial approach. Further, although Cragg describes the method as being percutaneous, the method still requires an access opening of at least 22 mm to accommodate the implant. The larger a surgical exposure is, the greater the likelihood of attendant bleeding and injury to local muscular, ligamentous, vascular and nervous tissues and in the lumbar region, the bowels may also be damaged.
Any device that would more easily, and/or more effectively, and/or more safely treat degenerative disc disease would be useful in the management of hundreds of thousands of suffering individuals. The current invention is an improvement to current systems and methods of performing interbody fusion because it enables surgeons to finally perform a true percutaneous interbody fusion at all levels of the spine.
The entire content of each and all patents, patent applications, articles and additional references, mentioned herein, are respectively incorporated herein by reference.
The art described in this section is not intended to constitute an admission that any patent, publication or other information referred to herein is “prior art” with respect to this invention, unless specifically designated as such. In addition, this section should not be construed to mean that a search has been made or that no other pertinent information as defined in 37 C.F.R. § 1.56(a) exists.